KENNEDY SPACE CENTER, FLA. - An Orbital Sciences L-1011 aircraft arrives at the Cape Canaveral Air Force Station Skid Strip. Attached underneath the aircraft is the Pegasus XL Expendable Launch Vehicle, which will be transported to the Multi-Payload Processing Facility for testing and verification. The Pegasus will undergo three flight simulations prior to its scheduled launch in late January 2003. The Pegasus XL will carry NASA's Solar Radiation and Climate Experiment (SORCE) into orbit. Built by Orbital Sciences Space Systems Group, SORCE will study and measure solar irradiance as a source of energy in the Earth's atmosphere. .